1. Field of the Invention
The present invention relates to a sound absorption sheet for a motor vehicle and an engine under cover for a motor vehicle using the sound absorption sheet.
2. Description of the Related Art
Conventionally, in a motor vehicle, there has been proposed an under cover for an engine or an engine under cover disclosed in, for example, Japanese Patent Laid-Open Publication No. 2001-10544. The engine under cover is disposed at the bottom part side of an engine, and a large number of small projections are formed on an inner wall face of the engine under cover at its engine side.
According to such a construction, when noises generated from the engine enter a large number of the small projections at the inner wall face of the engine under cover, the noises are irregularly reflected by a large number of the small projections. Thus, sounds reflected by the irregular reflection interfere to each other and are offset or cancelled out to each other. As a result, reduction of noises shall be able to realize sound absorption by the engine under cover without a sound absorption material.
In the engine under cover constructed as above, a large number of the small projections are merely formed on the inner wall face of the engine under cover at its engine side, as described above. Thus, even if a large number of the small projections are formed respectively into a semispherical shape and regularly arrayed on the inner wall face of the engine under cover, it may be difficult to reduce the noises favorably with the above-mentioned mere cancellation of the sounds reflected to each other. This means that a large number of the small projections lack sound absorption performance. As a result, there is caused the drawback that absorption of noises cannot be favorably secured by a large number of the small projections.